High frequency saw filters stretched over non-overlapped electrodes for satellite broadcast receivers

We have developed a new UHF SAW filter for satellite broadcast receivers. The features are a high center frequency which suppresses image inter-ference, sufficiently flat group delay for linear FM detection, and no necessity to adjust for tuning. The influence of electrode resistance on insertion loss, and the triple transit echo caused by surface wave reflection have been analyzed in Smith's extended equivalent circuit model, and in our research is effectively applied as an independent design parameter of radiation and load conductance. In consequence interdigital transducers with wide apertures stretched over the nonoverlapped electrodes have been applied to suppress undesired surface wave diffraction and reflection effects without any increase of insertion loss, and they therefore eliminate the convenventional tuning coils.